Belt spool for a belt retractor, and belt retractor

ABSTRACT

A belt spool for a belt retractor with a force limiter has at least one flange ( 16 ) with a front face ( 27 ) and one insert ( 28 ) provided on the front face ( 27 ) of the flange ( 16 ). The insert ( 28 ) constitutes the portion that is cut by the force limiter. The invention further relates to a belt retractor.

TECHNICAL FIELD

The present invention relates to a belt spool for a belt retractor andto a belt retractor.

BACKGROUND OF THE INVENTION

Disclosed in the prior art are belt retractors having force limiterswhich, once a specific belt webbing withdrawal force in the safety beltis exceeded, allow a rotation of the belt spool in spite of the beltspool being blocked. This limits the forces exerted on a vehicleoccupant by the safety belt.

DE 103 43 534 A1 shows a belt retractor in which, in addition to a firstforce limiting device which contains a torsion bar, a second forcelimiting device may be active at the same time which uses a materialcutting process. In particular by means of the cutting width and cuttingdepth parameters, a progressive, degressive or constant evolution of thelevel of force is allowed in sections.

The invention provides a belt spool which allows the force level to beadjusted more flexibly. The invention furthermore provides a beltretractor including a force limiter the force level of which can beadjusted more flexibly.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a belt spool for a belt retractor with aforce limiter has at least one flange and one insert provided on thefront face of the flange, the insert constituting a portion that is cutby the force limiter. According to the invention, the belt spool is notmade in one piece, but that portion which is cut by a force limiter isin the form of an insert part. The basic idea is that the material thatis used for the separate part is different from the material that isused for the belt spool. The insert may be made of different materialshaving respectively different mechanical properties and may havedifferent contours. In this way, the cutting width and cutting depth ofthe force limiter, which is more particularly a cutting body, may bevaried, which changes the level of force and its evolution.

Preferably, a bead having an axial height and a radial width is providedon the insert. The height and the width of the bead may be used toadjust the force level and the evolution thereof.

The axial height and the radial width of the bead may vary at least insections, so that with an increasing cutting width and/or cutting deptha progressive evolution may be achieved and with a decreasing cuttingwidth and/or cutting depth a degressive evolution is achieved.

More particularly, the insert is fastened to the belt spool. The insertis glued to or pressed into the belt spool, for example. The insert mayjust as well be placed into the casting mold of the belt spool. Whencasting is completed, the insert is integrally cast with the belt spool.

Preferably, the insert is made of steel. Steel is suitable to be cutuniformly. If the steel is heat-treated, the strength of the insert mayvary in sections, resulting in a change in the depth of cut of a cuttingbody, which will lead to a variation in the evolution of force.

The present invention further relates to a belt retractor comprising aframe, a belt spool of the type mentioned above which is rotatablymounted in the frame, a force limiter, and a disk which is adapted to beblocked at the frame so as to be non-rotatable relative thereto. Asregards the advantages, reference is made to the explanations above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional view of a belt retractor with a beltspool and a force limiter;

FIG. 2 shows a perspective view of a belt spool for a belt retractoraccording to the prior art; and

FIG. 3 shows a perspective view of a belt spool according to theinvention for a belt retractor.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

The belt retractor shown schematically in FIG. 1 includes a frame 10 anda belt spool 12 rotatably mounted in the frame 10. Belt webbing 14 canbe withdrawn from the belt spool 12. A flange 16 of the belt spool 12has a disk 18 applied thereto which, by a blocking mechanism 20, can becaused to rest at the frame 10 so that rotation is prevented. The disk18 may be connected with the flange 16 of the belt spool 12 by shearpins 22 for joint rotation up to a specific torque.

Arranged in the hollow interior of the belt spool 12 is a torsion bar 23which is coupled at one axial end for joint rotation with the disk 18and at the opposite end for joint rotation with the belt spool 12.

On its side facing the flange 16 the disk 18 has a recess in which acutting body 24 is inserted. The cutting body 24 protrudes axiallybeyond the face of the disk 18 facing the flange 16.

A bead 26 is formed in the front face 27 of the flange 16 facing thedisk 18 (cf. FIG. 2), the cutting body 24 projecting into the bead 26.

When a locking is activated in a vehicle-sensitive or beltwebbing-sensitive manner, the blocking mechanism 20 blocks the disk 18on the frame 10 of the belt retractor so as to prevent rotation. Thisalso locks the belt spool 12 so as to be locked in rotation on the frame10 via the torsion bar 23, but only up to a belt load in which as yet notorsion of the torsion bar 23 occurs. As soon as this belt load isexceeded, the belt spool 12 will rotate in relation to the disk 18 andthe torsion bar 23 will be twisted at the same time. In this relativerotation the cutting edge of the cutting body 24 will come intoengagement with the material of the flange 16 of the belt spool 12. Anyfurther relative rotation is possible only by the cutting body 24cutting a chip from the bead 26. This means that a conversion of energytakes place by a cutting of material, which occurs in parallel to theconversion of energy by the torsion bar 23 being twisted.

FIG. 3 shows the belt spool 12 according to the invention, which may beinserted into a belt retractor. The components already mentioned aredenoted by the same reference numerals, and reference is made in thisrespect to the explanations above.

The belt spool 12 differs from the belt spool 12 described withreference to FIGS. 1 and 2 in that an annular insert 28 made of steel isprovided on the flange 16 facing the disk 18. The insert 28 isadhesively fastened to the belt spool 12. The insert 28 may just as wellbe placed into a casting mold for the belt spool 12. When casting iscompleted, the insert is integrally cast with the belt spool 12. Theinsert 28 could also be pressed into the spool body.

The insert 28 includes the bead 26 which has already been discussed andfrom which the cutting body 24 can cut a chip. In the embodiment shown,the radial width B of the bead 26 decreases along the cutting path, sothat a degressive evolution of the force level is attained. The radialwidth could just as well increase, which would result in a progressiveevolution, or the axial height could decrease or increase. Further, theaxial height H (see FIG. 1) could vary.

The insert 28 made of steel is cut more uniformly than the brittle castmaterial of the belt spool, which was cut in the prior art. Diecastaluminum or diecast zinc serves as the casting material for the beltspool.

The mode of functioning of the belt retractor is the same as thatexplained above, reference being hereby made thereto.

1. A belt spool for a belt retractor with a force limiter, comprising at least one flange (16) with a front face (27) and one insert (28) provided on said front face (27) of said flange (16), said insert (28) constituting a portion that is cut by said force limiter.
 2. The belt spool according to claim 1, wherein said insert (28) is substantially annular.
 3. The belt spool according to claim 1, wherein a bead (26) having an axial height (H) and a radial width (B) is provided on said insert (28).
 4. The belt spool according to claim 3, wherein said axial height (H) and said radial width (B) of said bead (26) vary at least in sections.
 5. The belt spool according to claim 1, wherein said insert (28) is fastened to said belt spool (12).
 6. The belt spool according to claim 1, wherein said insert (28) is made of steel.
 7. A belt retractor comprising a frame (10), a belt spool (12) according to claim 1 which is rotatably mounted in said frame (10), a force limiter, and a disk (18) which is adapted to be blocked at said frame (10) so as to be non-rotatable relative thereto.
 8. The belt retractor according to claim 7, wherein said force limiter is a cutting body (24) adapted to cut said insert (28). 